The present invention relates to a multi-channel mobile radio transmitter wherein call connection for mobile originating and/or mobile terminating is controlled through a common control channel, and more particularly, to a transmitter control system capable of preventing interference caused by the failure of the transmitter.
In the conventional multi-channel mobile radio communication system of this type, if the transmitter of a mobile telephone equipment continues transmission on a certain common control channel in the event of a failure of the transmission control circuit or switch circuit in the transmitter, for example, the connection control for all other mobile telephone equipments within the system is disturbed, resulting in a total system down.
To prevent such a malfunction a method has conventionally been known in which a transmitter on/off signal from the transmitter output control circuit is compared with a detected output signal from the FM transmitter by a comparator, and the output of the comparator drives a switching circuit so as to switch the power of the frequency generator. In this circuit arrangement, in the event of a failure of the transmitter such as transmission without a transmitter-on signal, the frequency generator is disabled so as to cut off the transmitter output power. In this expedient, however, if control signal lines between the transmitter output control circuit and the switch circuit are broken or short-circuited, the power supply to the frequency generator cannot be switched off and the FM transmitter continues transmission on the common control channel to cause the interference that results in a total system down.